Multi-scale numerical simulation method of hydraulic fracturing based on implicit level set

Abstract

The present invention proposes a multi-scale numerical simulation method for hydraulic fracturing cracks based on implicit level sets, comprising: modeling hydraulic fracturing cracks and constructing a linear elastic hydraulic fracturing model based on three-dimensional plane fractures; solving elastic fluid mechanics equations based on the linear elastic hydraulic fracturing model; solving nonlinear elastic fluid mechanics equations by converging elastic fluid mechanics equations to obtain the proximal asymptotic solution of the stable motion hydraulic fracturing cracks; and establishing a multi-scale numerical simulation system for hydraulic fracturing cracks based on implicit level sets to verify the asymptotic solution. Based on the construction of a linear elastic hydraulic fracturing model for three-dimensional plane fractures, the present invention proposes a multi-scale numerical simulation method for hydraulic fracturing cracks based on implicit level sets, adopts a fixed-point iteration method of the elastic fluid mechanics equations, and establishes a numerical simulation system. This system has practical significance for improving the ultimate recovery rate in the oil and gas well development domain, and can provide support for the subsequent efficient development of oil and gas wells.

Description

Technical Field

[0001] The present invention relates to the technical field of oil and gas well development, and in particular to the technical field of simulating the natural propagation or response of fluid-driven cracks in the upper crust, and specifically to a multi-scale numerical simulation method for hydraulic fracturing cracks based on implicit level sets. Background Art

[0002] my country is currently in a critical period of accelerating its development into a powerful nation, creating significant growth opportunities in oil and gas well development. Numerical simulation and analytical research on hydraulic fracturing in horizontal wells in gas fields is a key technical bottleneck in achieving efficient oil and gas well development and improving ultimate gas reservoir recovery. Foreign countries have developed gas field production enhancement technologies based on different reservoir characteristics, such as mechanical parameters, connectivity, lithology, and natural fractures. Following the lead of North America in achieving the "shale gas revolution," major domestic oil and gas fields are conducting research on tight oil and gas reservoirs. These technological advances have been applied to the Changqing Oil and Gas Field, achieving promising results and increasing both initial production and ultimate recovery.

[0003] In recent years, with the widespread adoption of high-performance computing across various fields, the modeling and simulation of hydraulic fracturing has advanced significantly. Consequently, a simulation system approach is needed that can further reduce oil and gas well production costs, ease construction difficulties, and fully account for factors such as natural fracture development, rock mechanical characteristics, and in-situ stress. Summary of the Invention

[0004] In view of the shortcomings of existing technologies, this paper considers the environmental characteristics of oil and gas wells and, based on the principles of elastic mechanics and mathematical tools, proposes a multi-scale numerical simulation method for hydraulic fracturing fractures based on implicit level sets, taking into account the development of natural fractures, rock mechanical characteristics, and ground stress. Based on the principles of elastic mechanics and mathematical tools, this paper constructs a linear elastic hydraulic fracturing model of three-dimensional planar fractures and proposes a multi-scale numerical simulation method for hydraulic fracturing fractures based on implicit level sets. Finally, using Python libraries such as NumPy and SciPy, as well as Matplotlib and Scikit-Learn, a numerical simulation system is established using a fixed-point iteration method for elastic fluid dynamics equations.

[0005] The technical solution of the present invention is: a multi-scale numerical simulation method of hydraulic fracturing cracks based on implicit level sets, comprising the following steps: modeling hydraulic fracturing cracks, constructing a linear elastic hydraulic fracturing model based on three-dimensional plane cracks, and realizing the measurement of the multi-scale process of hydraulic fracturing cracks; solving elastic fluid mechanics equations based on the linear elastic hydraulic fracturing model to realize the numerical simulation of the multi-scale process of hydraulic fracturing cracks based on implicit level sets; solving nonlinear elastic fluid mechanics equations by converging elastic fluid mechanics equations to obtain the proximal asymptotic solution of the stable motion hydraulic fracturing cracks; and establishing a multi-scale numerical simulation system of hydraulic fracturing cracks based on implicit level sets to verify the asymptotic solution.

[0006] The beneficial effects of the present invention relative to the prior art are:

[0007] The multi-scale numerical simulation method provided by the present invention targets the multi-scale behavior of planar hydraulic fractures in three-dimensional elastic media, and utilizes the natural propagation or response of fluid-driven fractures in the upper crust to simulate the process. This can further reduce the cost of oil and gas well production and ease construction difficulty. It has practical significance for improving the ultimate recovery rate in the oil and gas well development domain, and can provide core key technical support for the subsequent efficient development of oil and gas wells.

[0008] The multi-scale numerical simulation method provided by the present invention solves nonlinear elastic fluid dynamics equations by aggregating elastic fluid dynamics equations, and strikes a balance between computing resources and computing time.

[0009] The multi-scale numerical simulation method provided by the present invention does not require re-gridding as the fracturing process changes in time and space, and the calculation process is simpler and more efficient.

[0010] The multi-scale numerical simulation method provided by the present invention, based on the application of a fracture front state classifier, fully considers the coupling characteristics between fluid flow, leakage, elasticity, flow velocity history information and their states, and achieves optimized operation of the entire simulation process through comprehensive scheduling of computing resources and computing time.

[0011] The multi-scale numerical simulation method provided by the present invention has good simulation consistency, ensuring that the data used is consistent with the actual situation, eliminating deviations and inconsistencies, thereby improving the reliability and effectiveness of the simulation and reducing system risks.

[0012] The multi-scale numerical simulation method provided by the present invention has a relatively sophisticated multi-scale fracture behavior modeling capability, can simulate the multi-scale process of hydraulic fracturing cracks, improves the simulation accuracy, and provides core key technical support for the subsequent efficient development of oil and gas wells.

[0013] It should be understood that the implementation of any embodiment of the present invention does not mean that multiple or all of the above-mentioned beneficial effects must be possessed or achieved at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for the embodiments or the description of the prior art. Obviously, the drawings described below are merely exemplary, and those skilled in the art can, without inventive effort, derive other implementation drawings based on the provided drawings.

[0015] The structures, proportions, sizes, etc. illustrated in this specification are intended solely to complement the contents disclosed herein and to facilitate understanding and reading by persons skilled in the art. They are not intended to limit the conditions under which the present invention may be implemented and therefore have no substantive technical significance. Any structural modifications, changes in proportions, or adjustments in sizes, provided they do not affect the efficacy and objectives of the present invention, shall remain within the scope of the technical contents disclosed herein.

[0016] Figure 1 Schematic diagram of the overall principle framework of a multi-scale numerical simulation of hydraulic fracturing fractures based on implicit level sets in the present invention;

[0017] Figure 2 This is a schematic diagram of the overall process of a multi-scale numerical simulation method for hydraulic fracturing based on implicit level sets in the present invention;

[0018] Figure 3 A schematic diagram of a numerical analysis process according to an embodiment of the present invention;

[0019] Figure 4 Schematic diagram of a grid discretization method according to an embodiment of the present invention.

[0020] The same or corresponding symbols in the drawings indicate the same or corresponding parts. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention more clearly understood, the embodiments of the present invention are further described in detail below in conjunction with the embodiments and drawings. Here, the illustrative embodiments of the present invention and their descriptions are used to explain the present invention, but are not intended to limit the present invention.

[0022] It should be understood that the terms "comprises / comprising," "consisting of," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a product, apparatus, process, or method that includes a list of elements includes not only those elements but also, if necessary, other elements not explicitly listed, or elements inherent to such product, apparatus, process, or method. In the absence of further limitations, elements defined by the phrases "comprises / comprising," "consisting of," do not preclude the presence of additional identical elements in the product, apparatus, process, or method that includes the elements.

[0023] It should also be understood that terms such as "upper", "lower", "front", "back", "left", "right", "top", "bottom", "inside", and "outside" indicating directions or positional relationships are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device, component or structure referred to must have a specific direction, be constructed or operate in a specific direction, and should not be understood as limiting the present invention.

[0024] The implementation of the present invention is described in detail below in conjunction with preferred embodiments.

[0025] See also Figure 1 As shown in the principle block diagram, this invention constructs a linear elastic hydraulic fracturing model for three-dimensional planar fractures and proposes a multi-scale numerical simulation method for hydraulic fracturing fractures based on implicit level sets. Finally, a numerical simulation system is established using Python libraries such as NumPy and SciPy, as well as Matplotlib and Scikit-Learn, using a fixed-point iteration method for elastic fluid dynamics equations. This invention considers the environmental characteristics of oil and gas wells and, based on the principles of elastic mechanics and mathematical tools, fully accounting for natural fracture development, rock mechanical characteristics, and in-situ stresses, proposes a multi-scale numerical simulation method for hydraulic fracturing fractures based on implicit level sets.

[0026] See also Figure 2As shown in the flow chart, the present invention provides a multi-scale numerical simulation method of hydraulic fracturing cracks based on implicit level sets, comprising the following steps: S10, modeling hydraulic fracturing cracks, constructing a linear elastic hydraulic fracturing model based on three-dimensional plane cracks, and realizing the measurement of the multi-scale process of hydraulic fracturing cracks; S20, solving the elastic fluid mechanics equations based on the linear elastic hydraulic fracturing model, and realizing the numerical simulation of the multi-scale process of hydraulic fracturing cracks based on implicit level sets; S30, solving the nonlinear elastic fluid mechanics equations by converging the elastic fluid mechanics equations, and obtaining the proximal asymptotic solution of the stable motion hydraulic fracturing cracks; S40, establishing a multi-scale numerical simulation system of hydraulic fracturing cracks based on implicit level sets to verify the asymptotic solution. Based on the construction of a linear elastic hydraulic fracturing model of three-dimensional plane fractures, the present invention proposes a multi-scale numerical simulation method of hydraulic fracturing fractures based on implicit level sets, and adopts the fixed-point iteration method of elastic fluid mechanics equations to establish a numerical simulation system. This has practical significance for improving the ultimate recovery rate in the oil and gas well development domain, and can provide core key technical support for the subsequent efficient development of oil and gas wells.

[0027] The following describes the method steps of the present invention using a specific embodiment.

[0028] In step S10, hydraulic fracturing cracks are modeled, and a linear elastic hydraulic fracturing model based on three-dimensional plane cracks is constructed to achieve measurement of the multi-scale process of hydraulic fracturing cracks.

[0029] First of all, it should be noted that hydraulic fracturing is a measure to increase oil and gas well production with broad application prospects. Hydraulic fracturing is the main form of natural gas extraction, which requires the injection of a large amount of water mixed with chemicals into the shale layer for hydraulic fracturing to release natural gas.

[0030] In some embodiments, constructing a linear elastic hydraulic fracturing model based on a three-dimensional planar fracture may be specifically performed as follows:

[0031] In step S101, an elastic fluid dynamics equation is constructed to model the plane fracture process in the open mode as a hypersingular boundary integral equation related to the fracture width and the normal component of the traction vector.

[0032] In order to model the fracturing process of the plane fracture in time and space and obtain a better approximation of the physical process, the elastic fluid mechanics equation needs to be established in this step.

[0033] For a plane crack in a homogeneous isotropic material, the area , the elastic fluid dynamics equation is as follows (1):

[0034] ——(1)

[0035] in, is the normal component of the applied traction force, is the far-field original compressive stress, is the fracture width, is the plane crack area, For the moment, Plane crack area The horizontal and vertical coordinates in are Cartesian coordinates, is a plane strain modulus, that is, a coefficient related to the fracture material.

[0036] Set the contact conditions as follows (2):

[0037] ——(2)

[0038] in, is a value related to the inherent roughness of the generated crack, is the fluid pressure;

[0039] When a crack opens at a given coordinate, the corresponding fracture force is Equivalent to fluid pressure .

[0040] In step S102, a motion equation of the lubricating fluid in the crack is constructed. The fluid motion equation characterizes the approximate process of the lubricating fluid and characterizes the possible displacement of turbulence.

[0041] It should be noted that in order to model fluids such as water and air and determine the force exerted, it is necessary to establish the equations of motion for the lubricating fluid in the crack. These equations of motion for the lubricating fluid are independently linked to the equations of elastic fluid mechanics through the crack opening.

[0042] The motion equation of the lubricating fluid in the crack is as follows (3):

[0043] ——(3)

[0044] in, is the rate at which fluid leaks from the two opposite sides of the crack, is the leakage coefficient, is the fluid flux in the fracture, is the injection rate of the fluid, is the Dirac function, is the fracture width, is the fluid pressure, For the moment;

[0045] Considering possible turbulence, fluid flux It is related to the fluid pressure gradient as follows (4):

[0046] —— (4)

[0047] in, is the fluid viscosity, is the leakage rate, is the coefficient, To simplify the Fanning friction coefficient, it is defined as follows (5):

[0048] ——(5)

[0049] in, is the local Reynolds number, is the roughness length, for .

[0050] The leakage rate of the fluid is as follows (6):

[0051] —— (6)

[0052] in, is the Carter leakage coefficient and is related to the characteristics of the rock and the fluid in the fracturing process. t0 is the initial time.

[0053] In step S103 , boundary conditions are set and analyzed. The boundary conditions follow the principle that the in-situ normal stress of the fluid and the fracture front is large enough, the hydraulic fracture propagates in quasi-static equilibrium, and rectangular lithologic boundary conditions are introduced.

[0054] The boundary conditions are as follows (7):

[0055] ——(7)

[0056] in, is the fracture width, for The breaking front end of the moment.

[0057] In step S20, based on the linear elastic hydraulic fracturing model, the elastic fluid mechanics equations are solved to realize the numerical simulation of the multi-scale process of hydraulic fracturing cracks based on implicit level sets.

[0058] See also Figure 3 In some embodiments, a multi-scale process of hydraulic fracturing is numerically simulated based on a linear elastic hydraulic fracturing model, and the elastic fluid mechanics equation is solved using an implicit level set method, which can be specifically performed as follows:

[0059] In step S201 , the grid is discretized. The hydraulic fractures are discretized using a fixed Cartesian grid. The grid size is rectangular, and the grid size is set.

[0060] like Figure 4 As shown in FIG, the present invention first performs a mesh discretization process. At any time, it is divided into top cells (near the front) or channel cells. In the channel cells, the cell centers adjacent to the top cells are regarded as monitoring points to decouple the finite discretization from the near-top hydraulic asymptotics. For the fluid pressure at the fracture, is linear with respect to other nearby grids, as shown in Equation (8):

[0061] ——(8)

[0062] in, is the far-field original compressive stress, For unit In the unit The elastic contribution part in width is equal to the residual aperture.

[0063] The unit-centered finite volume method is used to discretize the motion equation of the lubricating fluid in the crack in Equation (3) as follows (9):

[0064] ——(9)

[0065] in, is the fluid flux across the cell edge, is the term representing the local compression of the fluid, is the gravity term, is the local fluid injection rate, The current moment unit The leakage contribution of .

[0066] In step S202, a distributed dislocation technique is used to set the fracture width in each unit to a piecewise constant value, so that the elastic fluid mechanics equation is located at the center of each unit in the current fracture.

[0067] In step S203, the finite volume method centered on the divided unit is used to discretize the motion equation of the lubricating fluid, and the reverse Euler time integration method is used to improve the stability of the solution process.

[0068] In step S204, the elastic fluid dynamics equation is solved.

[0069] In view of the nonlinear coupling characteristics of equations (8) and (9), the present invention provides the matrix form of the elastic mechanics equation, as shown in equation (10):

[0070] ——(10)

[0071] in, is the identity matrix, elastic block It is dense, is sparse, and is the corresponding compressibility effect term, , related to the injection source and the leakage term, is the fluid injection rate, is the leakage term, is nonlinearly related to the current fracture width increment, is the width within the channel unit, ,in is the fluid flux, is the gravity vector.

[0072] In step S205, the multi-scale propagation process of the fracture is simulated based on the implicit level set, where the implicit level set includes: a fully implicit form and an explicit form, wherein the explicit form includes a predictor corrector and the like.

[0073] Based on the elastic mechanics equation (10), the explicit active minimum width constraint is considered as follows (11):

[0074] ——(11)

[0075] in, is the leakage intensity matrix, is the identity matrix, the superscript Represents channel, superscript Represents proximal end, superscript Represents an activated unit, is the elastic parameter in the channel, is the width within the channel unit, ,in is the fluid flux, is the gravity vector;

[0076] The implicit level set method is used to solve Equation (11).

[0077] In step S206, the fracture front state classifier is used to classify the fracture front into a propagation or stagnation state.

[0078] The fracture front state classifier is used to classify fracture fronts into either propagation or stagnation states based on the conditions in equation (2). This classifier can improve simulation accuracy and optimize computing resources based on different situations. This is also a feature of the present invention.

[0079] In step S30, the nonlinear elastic fluid dynamics equation is solved by converging the elastic fluid dynamics equations to obtain the proximal asymptotic solution of the stable motion hydraulic fracture;

[0080] In some embodiments, a Python program, based on libraries such as NumPy and SciPy, solves nonlinear elastic-fluid dynamics equations by assembling them, balancing computational resources and computational time to obtain a proximal asymptotic solution for a stable hydraulic fracture. This system then establishes a multi-scale numerical simulation system for hydraulic fractures based on implicit level sets. Based on the application of a fracture front state classifier, this invention fully considers the coupling characteristics between fluid flow, leakage, elasticity, and velocity history information and their states, and optimizes the entire simulation process through comprehensive scheduling of computational resources and computational time.

[0081] In some embodiments, solving the nonlinear elastic-fluid mechanics equations by converging the elastic-fluid mechanics equations to obtain the proximal asymptotic solution of the stable hydraulic fracture can be specifically performed as follows:

[0082] In step S301 , a simulation model is loaded based on function libraries such as NumPy and SciPy.

[0083] In order to further improve the computational performance of numerical simulation, the present invention strikes a balance between development speed and computational speed, and adopts function libraries such as NumPy and SciPy for development.

[0084] In step S302, elastic fluid dynamics equations are collected based on Python language.

[0085] The present invention considers the elastic-hydrodynamic equation (10), which requires a dense matrix generated by the boundary elastic integral, and constructs an equation whose product of multiple matrices has a sparse finite matrix, which is a function of the current width estimation.

[0086] The compressed sparse column matrix provided by SciPy is used as a matrix variable to calculate the efficiency of the width and pressure of all cells in the fracture grid. The dot product procedure provided by SciPy for sparse matrix multiplication is used to calculate the efficiency of the width and pressure of all cells in the fracture grid.

[0087] Use standard 2D NumPy arrays as dense elastic matrices.

[0088] As the main unknown, when there is no width constraint, the elastic-hydrodynamic equations can be obtained.

[0089] In step S303, the elastic fluid dynamics equation is iterated at a fixed point based on NumPy and LAPACK, and a hydraulic fracturing asymptotic equation is included to obtain the proximal asymptotic solution of the stable hydraulic fracturing fracture.

[0090] In some embodiments, the elastic-fluid dynamics equations are solved using a fixed-point iteration method and converted into a series of linear equations, wherein the high-performance computing library LAPACK is used for the solution.

[0091] In step S40, a multi-scale numerical simulation system of hydraulic fracturing fractures based on implicit level sets is established to verify the asymptotic solution.

[0092] It should be noted that a multi-scale numerical simulation system was established, and the theoretical model was cross-validated with the computer calculation results to verify whether the asymptotic solution met the modeling requirements.

[0093] Finally, taking the modeling and simulation of the radial fracturing process in a uniform permeable medium as an example, the main method steps and solution calculation process of the present invention are further explained:

[0094] In step S10, first, an elastic fluid dynamics equation is designed and constructed. This equation models the planar fracture process in the open mode as a hypersingular boundary integral equation related to the fracture width and the normal component of the pulling vector. Secondly, the motion equation of the lubricating fluid in the fracture is established. Finally, the boundary conditions are set and analyzed.

[0095] Taking the modeling and simulation of radial fracturing in uniform permeable media as an example, the values in the specific calculation process are as follows: (Plane strain modulus) ranges from 30-38GPa, The value range of (Carter leakage coefficient) is .

[0096] Step S20 mainly includes the following solution processes: (1) grid discretization; (2) distributed dislocation technology; (3) reverse Euler time integration; (4) elastic fluid mechanics equations; (5) simulation of the multi-scale propagation process of the fracture based on implicit level sets; and (6) fracture front state classifier.

[0097] Taking the modeling and simulation of radial fracturing in uniform permeable media as an example, the values in the specific calculation process are as follows: , The value range is and at a fixed rate injection.

[0098] Step S30 mainly includes the following solution process: (1) loading the simulation model based on function libraries such as NumPy and SciPy; (2) collecting elastic fluid dynamics equations based on Python language; (3) fixed-point iteration of elastic fluid dynamics equations based on NumPy and LAPACK.

[0099] Taking the modeling and simulation of radial fracturing in uniform permeable media as an example, the values in the specific calculation process are as follows: The area of modeling and simulation m, and and Direction divides the corresponding units.

[0100] It is easy for those skilled in the art to understand that, under the premise of no conflict, the above preferred solutions can be freely combined and superimposed.

[0101] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A multi-scale numerical simulation method for hydraulic fracturing based on implicit level sets, characterized in that: The steps include: Model hydraulic fracturing cracks, construct a linear elastic hydraulic fracturing model based on three-dimensional plane cracks, and measure the multi-scale process of hydraulic fracturing cracks; Based on the linear elastic hydraulic fracturing model, the elastic fluid mechanics equations are solved to realize the numerical simulation of the multi-scale process of hydraulic fracturing fractures based on implicit level sets; By gathering the elastic-fluid mechanics equations, we solve the nonlinear elastic-fluid mechanics equations and obtain the proximal asymptotic solution of the stable hydraulic fracture. A multi-scale numerical simulation system for hydraulic fracturing fractures based on implicit level sets is established to verify the asymptotic solution; in The hydraulic fracturing crack modeling is performed to construct a linear elastic hydraulic fracturing model based on three-dimensional plane cracks to achieve measurement of the multi-scale process of hydraulic fracturing cracks, including: The elastic-hydrodynamic equations are constructed to model the planar fracture process in the open mode as a hypersingular boundary integral equation related to the fracture width and the normal component of the traction vector. Constructing a motion equation of the lubricating fluid in the crack, wherein the motion equation of the lubricating fluid represents an approximate process of the lubricating fluid and represents possible displacement of turbulence; Boundary conditions are set and analyzed, which follow that the in-situ normal stresses of the fluid and the fracture front are large enough, the hydraulic fracture propagates in quasi-static equilibrium, and rectangular lithologic boundary conditions are introduced.

2. The multi-scale numerical simulation method according to claim 1, characterized in that: For a planar crack area in a homogeneous isotropic material , the elastic fluid mechanics equation is as follows (1): ——（1） in, is the normal component of the applied traction force, is the far-field original compressive stress, is the fracture width, is the plane crack area, Plane crack area The horizontal and vertical coordinates in For the moment, are Cartesian coordinates, is a plane strain modulus, that is, a coefficient related to the fracture material; Set the contact conditions as follows (2): ——（2） in, is a value related to the inherent roughness of the generated crack, is the fluid pressure; When a crack opens at a given coordinate, the corresponding fracture force is Equivalent to fluid pressure .

3. The multi-scale numerical simulation method according to claim 1, characterized in that: The motion equation of the lubricating fluid in the crack is as follows (3): ——（3） in, is the rate at which fluid leaks from the two opposite sides of the crack, is the leakage coefficient, is the fluid flux in the fracture, is the injection rate of the fluid, is the Dirac function, is the fracture width, is the fluid pressure, For the moment; Considering possible turbulence, fluid flux It is related to the fluid pressure gradient as follows (4): ——（4） in, is the fluid viscosity, is the leakage rate, is the coefficient, To simplify the Fanning friction coefficient, it is defined as follows (5): ——（5） in, is the local Reynolds number, is the roughness length, for ; The leakage rate of the fluid is as follows (6): ——（6） in, is the Carter leakage coefficient, and t0 is the initial time.

4. The multi-scale numerical simulation method according to claim 1, characterized in that: The boundary conditions are as follows (7): ——（7） in, is the fracture width, for The breaking front end of the moment.

5. The multi-scale numerical simulation method according to claim 3, characterized in that: Based on the linear elastic hydraulic fracturing model, the elastic fluid mechanics equations are solved to realize the numerical simulation of the multi-scale process of hydraulic fracturing fractures based on implicit level sets, including: Grid discretization: hydraulic fracturing cracks are discretized using a fixed Cartesian grid with a rectangular grid size, and the grid size is set; Using distributed dislocation technology, the fracture width in each unit is set to a piecewise constant value, so that the elastic fluid dynamics equation is located at the center of each unit within the current fracture; The finite volume method centered on the division unit is used to discretize the motion equations of the lubricating fluid, and the reverse Euler time integration method is used to improve the stability of the solution process; Solve elastic fluid dynamics equations; Based on the implicit level set, the multi-scale propagation process of the fracture is simulated. The implicit level set includes: a fully implicit form and an explicit form, wherein the explicit form is a predictor corrector; The fracture front state classifier is used to classify the fracture front into either propagation or stagnation state.

6. The multi-scale numerical simulation method according to claim 5, characterized in that: The method of discretizing the hydraulic fractures using a fixed Cartesian grid includes: Fluid pressure at the fracture is linear with respect to other nearby grids, as shown in Equation (8): ——（8） in, is the far-field original compressive stress, For unit In the unit The elastic contribution part in width Equal to the residual aperture; The unit-centered finite volume method is used to discretize the motion equation of the lubricating fluid in the crack in Equation (3) as follows (9): ——（9） in, is the fluid flux across the cell edge, is the term representing the local compression of the fluid, is the gravity term, is the local fluid injection rate, The current moment unit The leakage contribution of .

7. The multi-scale numerical simulation method according to claim 6, characterized in that: The solution of the elastic fluid dynamics equation includes: Based on the nonlinear coupling characteristics of formulas (8) and (9), the matrix form of solving the elastic fluid mechanics equation is as follows (10): ——（10） in, is the identity matrix, elastic block It is dense, is sparse, is the corresponding compressibility effect term, , related to the injection source and the leakage term, is the fluid injection rate, is the leakage term, is nonlinearly related to the current fracture width increment, is the width within the channel unit, ,in is the fluid flux, is the gravity vector.

8. The multi-scale numerical simulation method according to claim 7, characterized in that: The multi-scale propagation process of the fracture is simulated based on the implicit level set, including: considering the explicit active minimum width constraint based on the elastic mechanics equation (10), as shown in the following equation (11): ——（11） in, is the leakage intensity matrix, is the identity matrix, the superscript Represents channel, superscript Represents proximal end, superscript Represents an activated unit, is the elastic parameter in the channel; The implicit level set method is used to solve Equation (11).

9. The multi-scale numerical simulation method according to claim 1, characterized in that: The method of solving the nonlinear elastic fluid dynamics equations by collecting the elastic fluid dynamics equations to obtain the proximal asymptotic solution of the stable hydraulic fracturing cracks includes: Load simulation models based on NumPy and SciPy function libraries; Based on Python language, collect elastic fluid mechanics equations; Fixed-point iteration of elastic hydrodynamics equations based on NumPy and LAPACK, including a hydraulic fracturing asymptotic equation, is used to obtain the proximal asymptotic solution of a stable hydraulic fracturing fracture.

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